How it works
Bra size is two measurements: the band, which goes around the ribcage under the bust, and the cup, which is the difference between the bust measurement and the band.
- Measure snugly under the bust, level all the way round — that is the band.
- Measure loosely around the fullest part of the bust.
- Subtract the band from the bust: each inch of difference is one cup size (1 in = A, 2 in = B, 3 in = C, and so on).
| Bust − band | Cup (US) | Cup (UK) |
|---|---|---|
| 1 in | A | A |
| 2 in | B | B |
| 3 in | C | C |
| 4 in | D | D |
| 5 in | DD | DD |
| 6 in | DDD / F | E |
| 7 in | G | F |
| 8 in | H | FF |
Sizes are UK. Above a D cup the letters diverge, so a US 34DDD is a UK 34E — check which system a label uses before buying.
Examples
Worked examples:
- Band 32 in, bust 35 in: 3 in difference — 32C.
- Band 34 in, bust 40 in: 6 in — 34DDD in the US, 34E in the UK.
- Band 30 in, bust 31 in: 1 in — 30A.
Sister sizes hold the cup volume while changing the band: 34C, 32D and 36B all fit a similar bust. If the band rides up, go down a band and up a cup.
Related: BMI Calculator, BMR Calculator, Bra Size Calculator.
UK Bra Size Calculator: frequently asked questions
- What is a UK DD in US sizing?
- A UK DD is also a DD in the US, but UK E = US DDD and UK F = US G.
- How should a bra band fit?
- Level all the way round and snug on the loosest hook, so you can tighten it as it stretches; the band, not the straps, should provide most of the support.
- How does UK sizing differ from US sizing?
Up to a D cup they match. Above that the UK uses DD, E, F, FF, G while the US uses DD, DDD, G, H — so a US 34DDD is a UK 34E.
- Should I round the band measurement?
Round to the nearest even number. UK bands run in even inches, so a 33-inch measurement usually means a 34 band.
- How often should I re-measure?
Any time your weight changes by a few kilograms, and at least once a year — band size in particular shifts with weight.